Spectroscopic Fourier methods for thickness measurements of thick uniaxialwafers, with dispersive birefringence, using polarimetric techniques

This letter describes the measurement of the thickness of a thick uniaxial sample with a dispersive birefringence, using Fourier methods and standard polarimetric techniques. The formalism is also similar to, and easily adapt ed to, non-normal incidence thin-film thickness measurements. In a previous paper, a spectroscopic half-wave method for uniaxial wafer thickness measu rements was investigated. A number of corrections for the dispersion had to be included in the analysis. It is demonstrated here that the fast Fourier transform over the recorded interval is a more robust measurement, with hi gher accuracy, and higher repeatability. The signal is treated as a standar d frequency modulated signal. An undoped thick wafer of 4H-SiC and doped 4H -SiC are studied as examples.